The sigmoid sinuses (left & right), within a human head, are 2 areas beneath the brain, which allow blood veins to span the area, from the center of the head downward. They drain from the transverse sinuses (under the back of the brain) to the internal jugular vein. See diagram (at right): labeled under the brain as "PARS SIGMOID." (for Latin: sigmoideus).
Each sigmoid sinus begins beneath the temporal bone and follows a tortuous course to the jugular foramen, at which point the sinus becomes continuous with the internal jugular vein.
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